so I would basically use the same file naming scheme as for camera originals from a camera?

so for an old photos that I scan I would use;

my name_Date of the scan_a unique file number_and append it with something like scan?

what should I use for a unique file number? something like if I make scans on 2-7-2012, name each file; Sossity_120207_0001_scan.tiff, Sossity_120207_0002_scan.tiff, & so on for each scan done on 2-7-2012?

what about variations on a particular file? ie a master from a web?

would this work? Sossity_120207_0001_scan_MF for master file? etc?

what about a photo that I scan in which I know who took the photo? would I append their name to the file? along with the date I scanned etc?

Yes, the examples You mentioned are usefull i think.All data about the images (subject, persons on it, when it's taken, etc) i would put into the metadata (XMP/IPTC fields), for most issues there is a specific field available. This can be done with viewers like Adobe Bridge or with DAM like Lightroom, Expression Media, etc.Roelof